PVC Pedal Launcher

[efinkg]

I have build a Pedal launcher for my Ryan Warbirds, just getting tired of the stress in hand launches. Now my questions:
1. Is any strengthening in order to make the launches successful?
2. I have a Dynaflite 2M upstart, is there some sort of a graph out there that shows how the pressure on the tubing increases as the stretching increases?
3. Does the power of the launch increase as the length of the tubing increases(assuming that the tubing is at the same percentage of strength)
4. Does the power of the launch increase if the tube is made into a circle, that is to say, doubled over on itself?

[efinkg]

I have build a Pedal launcher for my Ryan Warbirds, just getting tired of the stress in hand launches. Now my questions: I have done a few tests to try and answer my own questions.
[/QUOTE]1. Is any strengthening in order to make the launches successful?
2. I have a Dynaflite 2M upstart, is there some sort of a graph out there that shows how the pressure on the tubing increases as the stretching increases?[/QUOTE]
I still don't have answers for these, anyone else?

[/QUOTE]3. Does the power of the launch increase as the length of the tubing increases(assuming that the tubing is at the same percentage of strength)[/QUOTE]
This seems to be false, I was getting 5lb of pull at any length(25ft, 6ft, 1ft) at 300-350% stretch.
[/QUOTE]4. Does the power of the launch increase if the tube is made into a circle, that is to say, doubled over on itself?[/QUOTE]
I seem to be getting 2X the power for a given stretching with a doubled over tube.

Can anyone else validate these? Should I just pull the tube out at the field until I get the power I want, then stake it out there?

[fuelsguy]

Most of the people who have used a Bungee launcher, myself included, use approximately five times model weight as the tension on the line at the release. I use about 15 ft of surgical tubing and a 20 ft line for my launcher.
A positive angle of launch, 5 degrees or so will get some altitude before the tension is lost. (I get about five ft altitude with my bungee as the tension falls off quickly.)
Ivor

[efinkg]

Thanks, I am using 1-1.5 pounders, so 5-7LB should so it. From my tests I'm thinking maybe I should use ~10-20 ft of tubing doubled over. I'm still working on the line length.